ETSI has defined a number of communication standards so that suppliers can supply independently-designed equipment that supports the same technology and are able to inter-operate with equipment from other suppliers that is compliant with that standard. One such data communication standard developed by ETSI is the Digital Video Broadcasting-Terrestrial (DVB-T) standard (ETSI EN 300 744), which has been developed for digital television sets and set-top boxes.
A more recent variation of the DVB-T standard is the DVB-H standard (ETSI EN 302 304) that incorporates enhanced features to allow improved reception of digital video broadcasting services for mobile devices. The DVB-H standard is particularly adapted for receivers that are battery powered. It is also particularly adapted for use for use with receivers that are liable to receive transmissions at a variety of heterogeneous conditions and locations, such as indoor, outdoor, moving at pedestrian speed, within a moving vehicle, which require robust reception and signal processing techniques to reduce or eliminate errors in reception.
One feature that has been incorporated within the DVB-H standard that facilitates this aim of mobile reception is the use of Multi Protocol Encapsulated-Forward Error Correction (‘MPE-FEC’) of received data. MPE-FEC facilitates recovery of data by a receiver in situations of high data-packet loss, which can occur when a receiver is in a changing environment, for example when a receiver is moving. MPE-FEC regroups data into blocks (MPE-FEC frames) and performs forward error correction on these data blocks. For an efficient error correction mechanism, a common approach is to have MPE-FEC frames larger than 512 Kbits. Thus, a receiver operating within a DVB-H compatible system receives an MPE-FEC frame with up to 2 Mbit of data over a single channel in a relatively short time period, for example 200 millisecond.
Power saving is crucial. Digital video broadcast reception inherently consumes power from the battery even more than normal voice communication. To save power, the DVB-H standard has incorporated a technique of ‘time-slicing’. Time slicing is a mechanism that regroups data into bursts. A burst is a quantity of data that is sent in a small amount of time. The next burst is sent after a significant time delay, and so on. During this period of time, bursts from other channels, programs or applications are sent. This feature of the broadcast transmission offers a possibility to the DVB-H unit to repeatedly power off components/circuits of the DVB-H unit's receiver chain to increase battery life. Generally, within the DVB-H standard, bursts and MPE-FEC frames correspond. This means there are an integer number of complete MPE-FEC frames per burst.
In particular, as shown in FIG. 1, each burst 10 of the relevant channel has a high signal bandwidth 12 and is followed by a period referred to as ‘Off-time’ 14 with essentially zero bandwidth. The average bandwidth level 16 over several bursts and Off-times is equivalent to a constant level whose value affects the receiver power consumption and which is lower the shorter each burst is and the smaller each burst's bandwidth is.
Specifically, the transmission of DVB-H data is organized in MPE-FEC frames. As shown in FIG. 2, such an MPE-FEC frame according to the DVB-H standard consists of 255 columns and N rows (the standard specifies multiple choices for the number of rows any one of which can be adopted with the present invention). The first 191 columns are referred to as an application table 20 and contain the payload or information data. The last 64 columns are referred to as a Reed Solomon (‘RS’) table 22 and are used by a Reed Solomon decoder in the baseband processor of the receiver to correct possible errors in the application table and also in the RS table itself as received. The MPE-FEC frame is not sent in one piece but smaller fractions.
There is a need for further improvement in the baseband processor power consumption and/or its error correction.